JPH0880029A - Base drive circuit life detection method - Google Patents

Abstract

(57) [Summary] [Purpose] The life of the base drive circuit is detected before the normal operation of the motor by the power transistor. A method for detecting the life of a base drive circuit of a power transistor for driving a motor, wherein the power transistor is turned on and off before the motor is operated, and a current flowing through the power transistor and the motor at the time of turning on and off is detected. It is detected that the base drive circuit has reached the end of life when the time until the current reaches a predetermined current value exceeds a predetermined time when the current rises or falls.

Description

Detailed Description of the Invention

[0001]

FIELD OF THE INVENTION The present invention relates to a method for detecting the life of a base drive circuit of a power transistor.

[0002]

2. Description of the Related Art Conventionally, when current stops flowing through a power transistor due to an abnormality in the base drive circuit, the machine vibrates and torque ripple increases, resulting in overload, and the on time of the base drive circuit. When the length is shortened, the power transistors in the upper and lower arms of the power transistor bridge are short-circuited, or overcurrent or overshoot is generated, so these are detected as overload or overcurrent.

[0003]

However, if an overcurrent or an overload occurs, the power transistor may be damaged before the detection and protection, and there is a problem that the motor is burned due to the imbalance of the current. It is an object of the present invention to detect the life of the base drive circuit before the normal operation of the motor by the power transistor.

[0004]

In order to solve the above problems, the present invention provides a method for detecting the life of a base drive circuit of a power transistor for driving a motor, wherein the power transistor is turned on and off before the motor is operated, The base drive circuit is at the end of its life when the current flowing through the power transistor and the motor is detected at the time of turning on and off, and when the time until the current value reaches a predetermined current value exceeds the predetermined time when the current rises or falls. Detect that.

[0005]

By the above means, the abnormality of the power transistor base drive circuit can be obtained before the main circuit is operated and the normal operation is performed, so that the motor and the power transistor can be prevented from being damaged.

[0006]

DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS A concrete embodiment of the present invention will be described below with reference to FIG. In FIG. 1, 1 is a diode bridge, 2
Is a capacitor, 3 to 6 are power transistors, 7 is a motor, 8 is a microcomputer, 9 is a base drive circuit, and 10 is a current detector. The base drive circuit 9 is connected to the base of each power transistor as shown in the figure, and although not shown, it becomes abnormal when the capacitors, photoisolators, etc. in it deteriorate and reach the end of their life. That is, in the case of a capacitor, the capacitance decreases due to deterioration,
When used in an on-delay circuit, etc., the on-time becomes shorter. In the case of a photo isolator, the amount of light is weakened due to deterioration of the light emitting element and the like, which delays the on / off time of the current of the power transistor. The microcomputer 8 controls the normal operation of the motor 7 or controls the base drive circuit according to the detected current from the current detector 10. The operation of the base drive circuit life detection circuit of the power transistor configured as described above will be described with reference to the flow of FIG. 2 and FIG. First, in step 1, the transistor 6 is turned on while the main circuit power is on (the capacitor 2 has an output), and the transistor 3 is turned on to delay the delay time To.
nd1 is turned off to obtain the delay time Toffd1. In step 2, while the transistor 5 is still ignited, the transistor 4 is first turned on to obtain its delay time Tond2, and turned off to obtain its delay time Toffd2. In step 3,
Similarly, the transistors 5 and 6 are turned on and off, and the delay times Tond3, Toffd3, Tond4, and Tof are delayed.
Get fd4. For example, if a small current that does not drive the motor is issued by issuing a command for power transistor ignition as shown in FIG. 3, for example, from the command on time until the current reaches 90% of the current command value. Delay time T
get ond. Similarly, the delay time Toffd from the command off time to the time when the current value becomes 10% is obtained. Next, in step 4, each delay time Tond1 to T4, T
Comparing offd1 to 4 with a predetermined threshold level of delay time, if all are below that level and normal, and if even one of each delay time is above the threshold level, the power transistor base drive circuit life And

[0007]

As described above, according to the present invention, it is possible to detect an abnormality in the power transistor base drive circuit before operating the main circuit, and since it is confirmed for each transistor, which transistor is selected. It is possible to know the base drive circuit of and to prevent damage to the motor and power transistor.

[Brief description of drawings]

FIG. 1 is a configuration diagram of a specific embodiment of the present invention.

FIG. 2 is a flow chart showing the operation of the present invention.

FIG. 3 is a timing diagram of commands and currents of a power transistor.

[Explanation of symbols]

 1 Diode Bridge 2 Main Capacitors 3, 4, 5, 6 Power Transistor 7 Motor 8 Microcomputer 9 Base Drive Circuit 10 Current Detector

Claims (1)

[Claims] 1. A method of detecting the life of a base drive circuit of a power transistor for driving a motor, comprising: turning on and off the power transistor before the operation of the motor;
The base drive circuit is at the end of its life when the current flowing through the power transistor and the motor is detected at the time of turning on and off, and when the time until the current value reaches a predetermined current value exceeds the predetermined time when the current rises or falls. A method for detecting the life of a base drive circuit of a power transistor for detecting the fact.